This application claims the priority of European Patent Application No. DE 101 00 119.3 filed Jan. 3, 2001, which is incorporated herein by reference.
The invention relates to a combination molding/punching station for molding and punching containers out of a foil strip consisting of a thermoplastic synthetic material. More particularly, the present invention relates to a molding/punching station for molding and punching containers out of a foil strip of thermoplastic synthetic material, with the station including a pivoting molding table for holding one of the tool halves, wherein the table is pivoted around a fixed axis of rotation and is guided along a guideway.
According to German reference 199 21 668 A1, the molding table for a combination molding/punching station is guided with a locally fixed rotating joint/sliding joint, and the rotational movement as well as short linear movements in the end positions are realized with a guideway. A pivoting lever engages in the region of the curve rollers and performs the lifting and pivoting movement. With this embodiment and relative to the point of rotation, the guideway is located on the side facing away from the foil strip. Additional guides are necessary to achieve an exact guidance of the tool, as is required in particular for the punching out of the formed containers. Guides are also necessary for maintaining the exact positioning of the molding table, which has been pivoted to a location in front of the stacking table. However, the known guides become effective only in the end positions. Before the end positions are reached, the threat of vibrations exists because the lever ratio between the distances the center of gravity and pivoting point or pivoting point and support by the curve roller changes constantly. The lever ratio becomes increasingly unfavorable during the approach to the end positions of the molding table. Vibrations and force changes of this type result in wear and tear on the positioning and guide parts as well as the drive.
Another disadvantage of this type of design is that no direct cross-connection is possible between the shafts supporting the pivoting levers. An involved synchronizing device must be provided underneath the molding table, which transmits the force to the pivoting levers, arranged on both sides of the molding table, and which synchronizes the movement sequence. Synchronizing devices of this type are very involved and always have some play, so that an identical lift of the molding table on both sides is not a given.
A molding/punching station is known from Canadian Patent Reference No. 2 240 428 A1, which uses three curved paths to achieve a pivoting movement as well as linear movement sequences in the end positions. The expenditure for producing these curved paths, which must be synchronized exactly, is very high. The curve roller diameter is limited because the curved paths or curved path sections will otherwise converge. Nevertheless, narrow regions develop locally between the curved path sections that are sensitive to breakage because high forces act upon these regions via the curve rollers. During the movement along the curved paths, the curve rollers are subjected to a change in direction, which reduces their service life as well as that of the curved path.
It is the object of the invention to improve the support and guidance of the molding table during its complete pivoting movement while retaining the advantage that the distance between the center of gravity and the pivoting point is initially reduced during the pivoting movement and subsequently increases again toward the end of the movement sequence. The wear and tear of components should be reduced. Both levers for starting the pivoting movement should be arranged on a transversely extending shaft, so that an involved synchronization that involves play can be avoided. The device should have a simple configuration and the guide parts should have a simple design.
The above object generally is achieved according to the present invention by a molding/punching station for molding and punching containers out of a foil strip of thermoplastic synthetic material, which station includes a molding table for holding one half of a mold; a frame in which the table is mounted for pivotal movement about a fixed axis of rotation transverse to a longitudinal axis of the table; and a single guideway, mounted on the frame and engaging the table for guiding the pivotal motion of the table, to the features in claim 1, with the guideway for pivoting table being disposed between the plane of the foil strip in the station and the pivoting point or axis of rotation of the table, if necessary with sectional areas of the guideway being opposite the foil strip. With this type of arrangement, an effective guidance of the molding table, which can be pivoted, is always possible at a favorable location.
Different embodiments of the molding/punching station are described in further detail with the aid of the schematic drawings.